The present invention relates to an idling stop technique which automatically stops/starts an engine of a vehicle.
In recent years, for the purpose of saved fuel and reduced exhaust gas, an idling stop device which automatically stops/starts an engine of a vehicle while it is stopping for a relatively short time such as in a red light have been in practical use. For the vehicle equipped with such an idling stop device, the engine is stopped when a stop condition such as stepping on the vehicle's brake to transition its traveling state into its stop state is established, whereas the engine is automatically started when a start condition such as releasing the brake during the engine stop is established (for example, see JP-A-2009-13953).
Power to drive a starter motor to start an engine of a vehicle is supplied from a battery mounted within the vehicle. Since power required by the starter motor to start the engine may be very high, when engine stopping/starting by an idling stop function is repeated as a battery voltage is decreased, the battery voltage may be further decreased to be so low that the engine cannot be started. Accordingly, in a case where the battery voltage is decreased due to deterioration of the battery, there is a need of a measure to prevent deterioration of the battery voltage in order to start the engine with the idling stop function.
Alternatively, in a case where the battery voltage is decreased due to deterioration of the battery, it is desirable to notify a user of information indicating deterioration of the battery to allow the user to replace the battery.
Further alternatively, in a case where the battery voltage is decreased due to deterioration of the battery, there is a need of a measure to increase the battery voltage.
As mentioned above, since power required by the starter motor to start the engine may be very high, the battery voltage may be greatly decreased when the engine is started. Accordingly, for example, a microcomputer mounted within the idling stop device is used to monitor the battery voltage when the engine is started by operation of a start switch by a user. At this time, if the battery voltage is decreased to be lower than a predetermined threshold value, it may be considered that the microcomputer executes a measure to prevent the battery voltage from being decreased when the engine is started with the idling stop function.
Alternatively, if the battery voltage is decreased to be lower than a predetermined threshold value, it may be considered to notify the user of the information indicating deterioration of the battery.
Further alternatively, if the battery voltage is decreased to be lower than a predetermined threshold value, it may be considered that the microcomputer executes a measure to increase the battery voltage.
However, since power to operate the microcomputer is also supplied from the battery, when an engine is started, if the battery voltage is significantly decreased to be lower than a voltage at which the microcomputer can operate, the microcomputer is reset without operating. The microcomputer reset in this manner and restarted cannot detect the cause of the reset and the battery voltage before being reset. The microcomputer may be reset even in situations other than decrease of the power voltage of the microcomputer, for example when the microcomputer falls into a runaway state; however, the microcomputer cannot detect the cause of such reset.
Therefore, even when the battery voltage is decreased such significantly that the microcomputer is reset, the reset microcomputer performs starting of the engine with the idling stop function without taking any measure to prevent the battery voltage from being decreased. As a result, the microcomputer is again reset, thereby disallowing the engine to be started.
In addition, even when the battery voltage is decreased such significantly that the microcomputer is reset, the reset microcomputer cannot recognize that the battery voltage is significantly decreased, and it is not possible to notify the user of the information indicating deterioration of the battery. As a result, the deteriorated battery is continuously used in the vehicle, thereby disallowing the engine to be started, eventually.
In addition, even when the battery voltage is decreased such significantly that the microcomputer is reset, the reset microcomputer repeats stopping/starting of the engine with the idling stop function without taking any measure to increase the battery voltage. As a result, the engine is disallowed to be started, eventually.